Somewhat odd behavior with fill( and color picker

Some folks accidentally write fill( on same line as next command. The following shows the color picker at the end of the line:
fill(ellipse(200, 150, 50, 50);
Then, if you use the color picker, it ends up overriding only part of the command, leaving the code in a state of fill( plus 4 parameters.

Relatedly, if you manage to delete the numbers and have a line like this:
fill(
Then if you do use the color picker, you get the numbers but not the closing parentheses.

I think that we probably shouldn't show the color picker unless the numbers are there? (Or, fix the results of using it in those 2 cases).

Start by reproducing the two examples in the live editor: `fill(ellipse(200, 150, 50, 50);` and `fill(`, then locate the color-picker handling for incomplete fill calls. Done means the picker is hidden or both cases preserve a complete, valid command with the expected numbers and closing parentheses.

Written by the indexing model from the issue text.